“Bring Back the King: The New Science of De-extinction” by Helen Pilcher (Bloomsbury Sigma)

Two years later, “cells with Celia’s DNA were injected into goat eggs that had been stripped of their own genetic material. After a brief electrical jolt, the eggs then began to divide.”

The embryos were implanted into the wombs of “surrogate mother goats,” and while most of the pregnancies failed, one did not.

History was made on July 30, 2003, when one of Celia’s clones was born, marking the first time a species ever came back from extinction. Sadly, her health did not hold up. Her lungs had been “grossly deformed” and she died seven minutes later — marking the first time ever a species had gone extinct twice.

Many of us were introduced to the concept of “de-extinction” by the movie “Jurassic Park,” which resurrected the dinosaurs to horrific ends.

But the idea behind the film wasn’t the wild invention of a Hollywood screenwriter.

Pilcher writes that in the 1980s, John Tkach, founder of a “secretive cabal of scientists and clinicians in Bozeman, Montana” calling themselves the Extinct DNA Study Group, posed an intriguing thought experiment.

“What if, many millions of years ago, there had been a hungry mosquito that dined on a dinosaur then became trapped in amber, with its last supper still inside its stomach. If one could recover a dinosaur blood cell from inside that mosquito and then transplant it into an egg that had had its own DNA removed,” it might be possible to “grow a dinosaur.”

This theory might have been far-fetched, but it wasn’t totally crazy. Entomologist George Poinar from the University of California at Berkeley spent his career studying million-year-old insects preserved inside tree resin that had hardened into amber. Usually they were intact on the outside but the insides were “a disappointing mess,” but in 1980, he came across a fly that “defied expectation,” with cells still intact after 40 million years. This was exactly what Tkach had theorized about.

A modern living dinosaur is not a fantasy.

Poinar’s findings, once published, excited the scientific community, including “a tall, gangly man” who visited his lab to ask questions about “bringing back life forms in amber.” Poinar thought nothing of it until years later, when he was informed that he’d been thanked in the back of a new book, soon to be a movie, called “Jurassic Park.” The book’s author, Michael Crichton, had been his tall, gangly visitor and “used [his visit] as the scientific basis for his novel.”

So where does the effort to de-extinct the dinosaurs sit today, decades later?

“A modern living dinosaur is not a fantasy,” writes Pilcher in her book.

But while there are respectable scientists who believe it can be done, she also makes it clear that we shouldn’t hold our breath. After all, finding the raw material to create a dinosaur is a tremendous challenge, to say the least.

“To de-extinct an animal, you need a source of that animal’s DNA,” writes Pilcher. “But all we have for dinosaurs are their remains, cast in stone.”

In 2000, a bucardo goat named Ceila died in Spain as the last of a species. Three years later scientists brought her back to life.Courtesy Government of Aragon

Much of our information on dinosaurs comes from fossils, and “dogma has it that when fossilization is complete, any organic trace of the animal is gone,” Pilcher writes.

Even so, starting in 1992, paleontologist Mary Schweitzer made a series of discoveries determining, among other things, that dinosaur fossils “contain molecules that are found in red blood cells,” and that certain types of dinosaur tissue could “survive fossilization.”

Continuing her work, she determined that protein molecules had survived as well, leading the Guardian newspaper to write that her findings “hint at the tantalizing prospect that scientists may one day be able to emulate ‘Jurassic Park’ by cloning a dinosaur.”

Still, this is just a first step in uncovering enough dinosaur material to build them anew.

“Although dinosaurs were made of protein (and many other molecules besides), we can’t somehow rebuild one from a few scrappy bits of collagen. It’s like trying to construct the 5,195-piece Lego Star Wars Millennium Falcon from just a few bricks and the picture on the box,” Pilcher writes. “Without the instructions, it’s impossible to know what the other bricks should be or how to put them together.”

These “instructions” are also known as DNA, and it’s still unclear how long such “a hopelessly flimsy molecule” can survive.

In the 1990s, a series of discoveries claimed to have retrieved DNA from as long as 120 million years ago, including from an 80-million-year-old dinosaur bone. These claims were debunked, however, by Nobel Prize-winning biochemist Tomas Lindahl, who showed that “because of the way DNA breaks down, it simply can’t survive over these kinds of time frames.”

Sam Neill’s character in “Jurassic Park” is based on real-life de-extinction scientist Jack Horner.reuters

His claim was proved in 2012 “by a study that found that DNA has a half-life of just 521 years.”

This means that “after 6.8 million years, every single link would be destroyed, making the recovery of DNA from fossils any older than this completely impossible.”

It turned out there had been no DNA in the fossils from the 1990s discoveries and that the experiments had accidentally “amplified bits of contemporary DNA from the surrounding environment.”

Recently, using more advanced detection equipment, scientists have been able to confirm that the oldest DNA found to date belonged to a “700,000-year-old horse found frozen in the Canadian permafrost,” and that the oldest human DNA came from a “400,000-year-old hominin (an older species of human) found in an underground cave in Spain’s Atapuerca Mountains.”

The dinosaurs went extinct around 65 million years ago. So while a recently announced find of a 99-million-year-old dinosaur tail that included bones, soft tissue, and feathers, all cast in amber, was exciting for scientists studying the ancient animals, DNA breakdown means it won’t help resurrect them.

Still, Schweitzer believes that discovering dinosaur DNA one day might be possible. “If you can get DNA from a 700,000-year-old fossil, why not a million-year-old one,” she told Pilcher, “and if you can get DNA from a million-year-old fossil, why not one that is 7 or even 70 million years old?”

Jack Horner, the inspiration for Niell’s character and the scientific advisor for the movie, wants to make evolution run backwards.FilmMagic

These types of searches have been Schweitzer’s life’s work, and she continues them to this day.

There are some scientists — including Schweitzer’s boss, Jack Horner, the scientific adviser for “Jurassic Park” and the inspiration for Sam Neill’s scientist character in the film — who wonder if it might be possible to resurrect dinosaurs in other ways.

“Horner believes he could make a dinosaur within as little as a decade without ever having to resort to ancient dinosaur DNA,” writes Pilcher. “All he has to do is make evolution run backwards.”

The first step of this scheme is to start with a modern descendant of the dinosaur. That is the easy part, as birds and alligators are the evolutionary descendants of the theropod, the category of two-legged dinosaur that includes the T. rex.

Horner’s notion involves taking an embryo of a modern bird and somehow culling out its ancient evolutionary characteristics, given that “sometimes living, modern creatures display distinctly ancient characteristics.”

Horner must find out what the instructions are and then discover a way of reactivating them, Pilcher writes.

“By tinkering with the development programs of embryonic chickens, he hopes to persuade them to bring out their inner dinosaur; to develop dinosaur-like features like teeth and tails.” In short, Horner is trying to hatch real-life chickens that are more dinosaur-like.

Even so, the odds of de-extincting the dinosaur are about as good as one showing up as your next Uber driver.

Scientists are currently trying to de-extinct species as diverse as the dodo, the passenger pigeon and the woolly mammoth but have hit road­blocks including a lack of DNA, no proper incubation environment and the risk of cruelty to living related species that would need to serve as surrogates. (See sidebar.)

On a more positive note, Pilcher writes that the science of de-extinction may help prevent endangered species from going extinct in the first place.

Pilcher writes that even if de-extinction never works, the efforts might help to save endangered species—like the northern white rhino, of which only three remain.Getty Images

“There are a number of projects out there where people are deliberately collecting cells from endangered animals, [including] collecting roadkill and taking cells from that,” says Pilcher. “We also have museums filled with all these stuffed animals, and while they don’t have living cells, very often they’ll have dead cells which have DNA.”

She notes, for example, that there are only three northern white rhino left in the world, which aren’t able to reproduce due to age and other factors.

Scientists have already taken skin cells from the rhinos in the hopes of one day converting the material first into stem cells, then into eggs that can be fertilized with semen samples, which they’ve also extracted.

According to Pilcher, it’s not inconceivable that scientists could breed a northern white rhino in a test-tube sometime in the next three to 10 years.

Meanwhile, if it’s dinosaurs you really want to see brought back to life, you’re better off marking your calendar for 2018, when the next “Jurassic Park” sequel is scheduled for release.